Centrifugal concentrators for biological applications

insights from industryAlison WakeProduct & Marketing ManagerGenevac

An interview with Alison Wake, Product & Marketing Manager, Genevac, conducted by April Cashin-Garbutt, MA (Cantab)

In life science labs around the world the task of concentration of a solute in a solution is commonly achieved using evaporator technology. Such technologies are also widely used in the concentration of pharmaceutical / natural product preparations using an extraction, precipitation and drying of the crude active agent protocol.

What biological applications are centrifugal concentrators most commonly used for?

Centrifugal concentrators are used to remove liquid, which could be water or an organic solvent, from a solution of a target material, leaving that material either in a more concentrated solution or as a dried product. There are many and varied applications for this technology, such as:

  • Molecular biology, where small volumes of water and ethanol need to be removed from DNA after precipitation, or PCR purification
  • Protein and peptide synthesis, which can use solvents for protein cleavage
  • Pre-analytical sample preparation for diagnostic, forensic and metabolic testing

When the target analyte is present in a very low concentration, i.e. below the level of detection of analytical equipment, then concentration is needed. This can mean concentration of a solvent after liquid or solid trace extraction or the actual direct concentration of the material to be tested itself, such as water or body fluids.

How do centrifugal concentrators work?

Centrifugal concentrators work by removing solvent under vacuum, so they're effectively boiling the solvent at a very low temperature. As the pressure in a system decreases, the boiling point of a solvent also decreases, allowing the solvent to boil and turn to a gas at a very low temperature. The solvent vapour is then either pumped away through the vacuum pump or condensed and trapped in a cold trap.

Simply applying a vacuum to a solvent in a tube can lead to gas bubbles forming anywhere within the tube. Think of the steam bubbles that form in a liquid when you heat it in a microwave. This bubbling and the resultant ‘solvent spitting’ is called bumping and it can lead to sample loss or cross-contamination.

To prevent this uncontrolled boiling, in a centrifugal concentrator samples are placed into a centrifuge and spun, this creates a pressure gradient within the solvent itself and that controls the boiling to the very top of the tube, preventing bumping.

Can you please give a brief overview of the new miVac range from Genevac?

Mivac centrifugal concentrators are capable of removing solvents from a variety of sample formats including tubes, microplates and vials. miVac concentrators can also be used to freeze dry aqueous samples.

miVac centrifuge

MiVac systems can be used with a wide range of solvents, from volatile organic types through to water and many medium boiling point solvents. There is a choice of three medium to high vacuum pumps and a dedicated DNA system with built-in pump.

Unique to miVac concentrators is SpeedTrap - a novel frost-free, refrigerated cold trap that minimises the traditional time required to dispose of removed solvent.

MiVac concentrators feature built-in special methods for working with alcohols, water and water mixtures to improve performance and optimise concentration times.

MiVac centrifugal concentrators are extremely quiet when in use and typical results with water show that they are up to 40% faster than other types of biological sample concentrators.

Who is the range aimed at?

The range is suitable for any scientist who wants to remove solvents from a number of samples in parallel. A miVac concentrator can accommodate a range of sample formats from microtitre plates to microcentrifuge tubes through various sizes of vials and test tubes up to the maximum of 50 ml.

While the miVac doesn't have all the features of Genevac high specification systems such as the EZ-2 Series or the HT Series and it can't accommodate the large volumes, which the Rocket can, it does offer at an entry level price - precise temperature control to protect samples during concentration and easy intuitive operation.

The miVac is particularly well suited to biological applications, where less aggressive solvents are often used and sample volumes tend to be smaller.

In what ways has the miVac range recently been updated?

The range has a slick new look with a distinctive cream and black color scheme. We've also introduced a new pressure controller, which is easy to program and has a graphical display of the vacuum level during the run. The pressure controller allows the highest specification quattro and super pumps options to be controlled at a suitable pressure for volatile solvent to be most efficiently removed.

Ramped sample concentration protocols can now also be programmed to further reduce the risk of bumping, particularly when solvent mixtures are used. Usefully the system can now also be programmed to dry aqueous HPLC fractions faster than before without freezing the water in them.

How does the miVac compare to competitor products in terms of speed and overall performance?

The ability to provide samples with sufficient energy to drive the evaporation process is key to high speed evaporation. Unique to an entry level concentrator - miVac systems have solid aluminium jet rotors which enable efficient thermal transfer. The energy is supplied as heat from the heated centrifuge chamber wall, which is efficiently absorbed by the solid Jet rotors and transferred into the samples through surface contact with the tube walls.

Centrifuge

Other concentrators use open rotors look like colanders and the tubes stick out through them rather than sit in the actual rotor. Open rotors don't provide the surface contact of a solid rotor and polypropylene rotors, which are common in competitor systems, can actively insulate the samples from the heat energy. Both of these designs result in a slower evaporation.

To further increase speed, miVac concentrators has special programs for water and less volatile solvents which are notoriously difficult to evaporate quickly. These programs periodically allow a little air into the system to aid the convection of heat from the chamber wall to the rotor and ultimately to the sample.

In summary, the combination of the solid aluminium rotors, special methods and an efficient cold trap to maintain vacuum means the miVac evaporation rates can be up to 200% faster than equivalent competitor systems.

It's important to note although we talk about efficient heat transferring to samples, the samples themselves don't actually get hot because the solvent is evaporating at a very low temperature due to the vacuum and the heat energy is immediately used in the evaporation process. So the actual samples themselves don't actually heat up.

Biological scientists are very conscious about heat and it's often a problem when we're trying to explain how these systems work. Any heat that gets to samples that are wet and evaporating simply drives the evaporation, it's immediately taken up turning the solvent into the solvent vapor, then it's taken away and condensed in the cold trap. That's where the heat ends up, it ends up being taken away by the cold trap and not introduced into the samples.

What design features make the miVac easy to use?

The miVac concentrators are designed to be very simple to use - they've just got one rotary control and the minimum of buttons/keys. The concentrator controls the pump automatically so you don't have to worry about switching that on at the correct moment and it's got timed runs, which means the system can be set to stop automatically.

As well as being very efficient at trapping solvent and vapours thereby improving evaporation rates, the miVac speed trap cold trap is very easy to use. It's a unique design, which ensures that solvents collect as a liquid in the collecting jug, which can then be removed, carried using it's built in handle and the solvent safely disposed of. The miVac Speedtrap also has an intermittent defrosting setting for water removal that means that the trap doesn't need defrosting at the end of the process and there's no downtime.

What feedback have you received from the biological market on the miVac range?

User feedback has been extremely positive and a common comment is that the miVac is a very easy system to use. Many users report that it has improved their workflow due to the increased evaporation rates and the ease of use.

In pre-analytical applications particularly, when labs have compared the miVac with systems using the blowdown evaporation method, they have found the miVac provides markedly improved recovery of volatile analytes. Interestingly some labs that were initially expecting the miVac to be slower than a blowdown system, in practice found evaporation rates to be comparable. We have a number of technical papers, which have been written by miVac users that illustrate how the system has improved their workflow and increased sample recovery.

What are some of the key benefits of using miVac?

Scientists are always looking to get the most out of any equipment they purchase and flexibility is important. Being able to use a piece of equipment for multiple functions is always welcome. Customers tell us the fact that the miVac can be configured to dry, concentrate and also freeze dry samples in one system is definitely a huge benefit.

Scientist's time is also very valuable and so being able to leave the concentration system to safely operate unattended, means they can go and do other tasks rather than having to simply sit and monitor samples as they concentrate.

Where can readers find more information?

About Alison Wake

ALISON WAKE BIG IMAGE

As Genevac Product and Marketing Manager I am responsible for product development and global marketing of the Genevac range.

Originally from a medical laboratory background, with an MSc in Applied Science from Sheffield University UK, I moved from the lab into the commercial sector in 1999.

I worked in several biotechnology and laboratory equipment supply companies, in both Scientific and Sales roles, before joining Genevac 11 years ago where positions have included Sales Consultant and Distribution Manager.

Genevac is a global leader in centrifugal evaporation systems and is part of SP Scientific, a leading manufacturer of specialty equipment for pharmaceutical, biotechnology and industry.

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The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of News-Medical.Net.
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